Full Idea
The 'undetected' or 'veiled' paradox of Eubulides says: if you know your father, and don't know the veiled person before you, but that person is your father, you both know and don't know the same person.
Gist of Idea
If you know your father, but don't recognise your father veiled, you know and don't know the same person
Source
report of Eubulides (fragments/reports [c.390 BCE]) by R.M. Dancy - Megarian School
Book Reference
'Encyclopedia of Classical Philosophy', ed/tr. Zeyl,Donald J. [Fitzroy Dearborn 1997], p.328
A Reaction
Essentially an uninteresting equivocation on two senses of "know", but this paradox comes into its own when we try to give an account of how linguistic reference works. Frege's distinction of sense and reference tried to sort it out (Idea 4976).
Related Idea
Idea 4976 The meaning (reference) of 'evening star' is the same as that of 'morning star', but not the sense [Frege]